Colloid Thermophoresis in the Dilute Electrolyte Concentration Regime: From Theory to Experiment

In this article, we developed a thermofluidic platform with femtonewton sensitivity to probe the interfacial interactions between silica microspheres and their surrounding fluid components. Using a theoretical model based on the Fokker-Planck equation, we studied the temperature and size dependencies of silica thermophoresis in dilute electrolyte solutions. In our model, electrostatic interactions are described by the mean-field Poisson-Boltzmann theory, while short-range hydrogen bonding interactions are characterized using a two-state statistical physics model, incorporating the flickering-clusters concept and mid-infrared spectroscopy data. In particular, the silica microspheres exhibit thermophilic behaviors over the experimental temperature range and the corresponding thermophoretic velocity increases in magnitude with increasing particle size. Throughout the paper, we show with experiments and theoretical calculations how the interplay between electrostatic interactions and hydrogen bonding interactions influences the thermophoretic behavior of silica microspheres at the molecular level.

Publications: Pu D, Panahi A, Natale G, Benneker A. Colloid Thermophoresis in the Dilute Electrolyte Concentration Regime: From Theory to Experiment. Soft Matter. 2023. https://doi.org/10.1039/D2SM01668K